In the photolithography process, exposure of a photoresist to UV light is an important step in attaining a high resolution image. With the continuing demand for smaller feature sizes in the semiconductor industry, 193 nm optical lithography has emerged very recently as the technology to produce devices with sub-100 nm features. The use of such a shorter wavelength of light requires the bottom antireflective coating (BARC) to reduce the reflection on substrate and dampen the photoresist swing cure by absorbing light that has passed though the photoresist. Commercially available antireflective coatings consist of both organic and inorganic based materials. Typically, the inorganic ARC, which exhibits good etch resistance, is CVD based and is subject to all the integration disadvantage of extreme topography; on the other hand, the organic ARC materials are applied by spin-on process and have excellent fill and planarization properties, but suffer from poor etch selectivity to organic photoresists. As a result, a material that offers the combined advantages of organic and inorganic ARC is highly desired.
In this regards, we have recently discovered that certain phenyl-hydride based silsesquioxane resins exhibit excellent anti-reflective coating properties for 193 nm light. Although Bottom Anti Reflective Coatings (BARC) materials can effectively reduce the reflection of activating radiation, removal of BARC materials without damaging the overlying photoresist and/or the underlying substrate has been very challenging. The typical process to remove BARC is by a plasma etch process. However, plasma etch often cause thinning of a photoresist layer. As a result, the patterns on the photoresist layer may be destroyed or becomes not transferable to the substrate layer. Plasma etch may also cause damage to the substrate thereby affecting the performance of the final device. What is more, the additional etch step for removing the BARC material increases cost and process complication in photolithographic practice. Therefore it is desirable to have an antireflective coating material that may be removed by means other than plasma etch.
This invention pertains to silsesquioxane resins useful as an antireflective coating layer for photolithography. This invention more specifically pertains to a silsesquioxane material containing carboxy moiety. The carboxy functional silsesquioxane resins form excellent spin-on film and are resistant to organic solvents such as PGMEA, 2-heptonene, but are developer-soluble when cured at 250° C. or below. In addition Si-rich ARCs produced from the carboxyl function silsesquioxane resins show excellent dry-etch resistance.